Process for the separation and recovery of iron and titania from ores and concentrates of same



United Stt sent inc 2,901,341 Patented Aug. 25, 1959 .Marvin J. Udy, NiagaraxFalls, N.Y., assignor to Strategic- Udy Metallurgical and Chemical Processes, LttL, Harn- -ilt0n, Ontario, Canada NoDrawing. Application October 14, 1957 Serial No. 689,786

14 Claims. (Cl. 75-40) invention relates to metallurgy, in general, and

has for an object the provision of an improved method or process for the production and recovery of iron and titania. More particularly, the invention contemplates the provision of an improved method or process. for the ous magnetites, and provides for the recovery of combined :titania and iron credits from such ores to an extent which renders possible the economical commercial utilization of these ores for their titania values.

In accordance with present commercial practices, titanium dioxide products are produced directly from naturally occurring minerals such as rutile ores of exceptionally high titanium dioxide contents, or from synthetic materials including beneficiated ores and concentrates, and furnaced slags of the type produced by the selective carbothermic reduction and separation of metallic iron from titaniferous iron ores. In the latter type operation as practiced heretofore, a primary titaniferous iron ore of ilmenite composition, or an ore concentrate, is reduced with carbonaceous reducing agents such as coke, coal, charcoal, etc., in the presence of various basic fluxing agents including limes-tone, lime, and the like, to

produce a metallic iron product and a slag rich in tita nium dioxide.

A variety of different fluxing practices have been employed heretofore in attempts to maintain fluid, workable slags within smelting operations conducted for the production of slag concentrates which are high in titam'um dioxide but low in iron oxide content. For example, one practice in relatively Wide use involves the utilization of basic fluxing agents such as lime, limestone, magnesia, etc., wherein the components of the furnace charge are so adjusted that for approximately each molar equivalent of acidic reacting material other than titanium dioxide within the resulting slag, there is included one molar equivalent of basic fluxing material, plus additional quantities of basic fluxing material in proportion to the molar content of titanium dioxide within the slag. Of course, the use of slags of this type in the manufacture of titanium dioxide products by acid decomposition techniques requires relatively large amounts of sulfuric acid, due in part to consumption of acid by the acid-soluble constituents of the slag. other than titania and chiefly the basic fluxes present within the slags. In the same manner, in recovery operations involving chlorination of the slags, the presence of large quantities of basic fluxes is undesirable for the reason that they are readily chlorina-table and result in wasteful consumption of chlorine.

Furthermore, it is impossible to eifect complete decomposition of these slags with the result that appreciable metallic values are lost in the formof a solid residue remaining from the acid digestion operation conducted for the formation of titanium sulfate. Attempts have been made to mitigate these disadvantages by the 'beneficiation or concentration of some ores to remove portions of the so-called undesirable acidic constituents, such as silica and alumina, prior to the smelting operations, thereby reducing the amount of basic iluxing material that must be added to the furnace to provide workable slags. In theory, it is presumed that the slags, to be digested most economically, must contain as small a proportion as possible of the acidic materials, principally silica and alumina.

in contrast to the foregoing theory, in my copending US; application Serial No. 553,529, filed December 16, 1955, now Patent No. 2,830,892, of which this application is a continuation-in-part, I have described and claimed fiuxing techniques designed to avoid the addition of large amounts of basic fluxing materials by utilizing an alumina-silica flux relationship to produce an irondegraded, titaniunrenriched acid slag which may be readily decomposed by acid leaching with the production and recovery of alumina and titanium dioxide as separate products.

Apart from the foregoing problems presented in connection with the after-processing of conventional titanium dioxide slags, a more important consideration presently confronting industry is that presented in connection with the actual furnacing of the slags due to their highly refractory nature. Thus, while basic fiuxing practices provide satisfactory fluid slags so long as they are maintained hot, the slags tend to chill rapidly and become highly viscous, thereby rendering it virtually impossible to effect complete settling and separation of metallic iron from the slags. The high temperature slags characteristic of such operations are extremely wearing on re fractory furnace linings and furnace roofs, and necessitate relatively frequent replacement of these items. Furthermore, in order to preserve the slags produced in accordance with heretofore customary practices in a fluid and workable state, extreme care must be exercised to maintain the titanium content of the slags principally within the dioxide form, i.e., to avoid over-reduction of the charge and the production of lower oxide forms of titanium therein. The formation of the sequioxide (Ti o l, for example, by reduction of titanium dioxide due to the action of carbonaceous reducing material added for iron removal, causes the slags to become viscons and gummy, whereas reduction of any appreciable portion of the dioxide to the monoxide form (TiO) renders the slags so highly refractory that they cannot be tapped from the furnace chamber. As a sum result of these difficulties, it is not at all uncommon to en counter so-called commercial titanium dioxide-enriched furnaced slags having residual iron contents within the range of from live to twelve percent by weight (5-12 wt. percent).

The present invention is based, in part, on my discovery that substantially all of the disadvantages customarily encountered in present practices for the processing of titaniferous iron ores can be overcome, and sig=v nificant advantages can be obtained, by utilizing alumina, exclusively, as the fluxing material for the formation of carbothermic reduction burdens containing such ores, and regulating the additions of the alumina flux solely on the basis of the titania content of the ores. Thus, I have found that the controlled addition of predetermined amounts of alumina to titaniferous iron ore furnace burdens, and the establishment of a fixed proportion of alumina with respect to the titania therein, results in the production of slags of excellent workability from which iron oxides present within the original ore can be reduced and separated to ultimate residual values within the range of one to two percent (l-2%) by weight. Furthermore, it is found that the synthetic titaniaalumina slag systems of the invention retain their desirable fluidity and general workability in spite of the fact that reduction smelting effected in the presence of excess carbonaceous reducing material for reduction of substantial quantities of titanium dioxide to lower oxides of titanium, such as Ti O and TiO, or even solutions of the monoxide and titanium carbide varying from thirty to sixty percent (30-60%) or more of the carbide. The resulting iron-free, titanium oxide-enriched alumina slags are found to be substantially completely digestible or soluble within conventional sulfuric acid leaching solutions, and those slags which are reduced to divalent forms of titanium (Ti-C and O) can be chlorinated directly to titanium tetrachloride to the extent of fifty percent (50%) or more of their titanium content, even in the absence of any added carbonaceous material. That is to say, by carefully adjusting the additions of alumina fluxing material and carefully controlling the amount of reducing agent added to an ore or concentrate undergoing smelting for iron removal, the percentage of divalent titanium (TiC and TiO) present within the resulting slag may approach one hundred percent of the total titanium content of the ore or concentrate. In this con nection, it is found that the lower grade titaniferous iron ores of relatively high alumina and silica contents are particularly amenable to complete conversion of their titanium contentto the divalent states. I

The process of the invention is applicable for use in connection with substantially all known types of titaniferous iron ores, including both highand low-grade materials. It is to be noted, however, that some ores of the general class described, notably the ilmenites, contain titania in such magnitude that one can obtain titaniaenriched slags of seventy-two percent (72%) or higher titania content solely by elimination of iron therefrom. On the other hand, in other types of ores, notably the magnetite formations (approximately 47% Fe and 12- 20% TiO the gangue materials present within the ores occur in such quantity and composition that the titanium content of the ores cannot be enriched, through iron removal, above approximately fifty-seven percent (57% While these latter ores are not economically suitable for commercial titania-recovery processing in accordance with present industrial practices, the relatively high-grade iron product recoverable therefrom in accordance with the process of the present invention and the additional credit obtained upon sale of this product, render such ores entirely practical for commercial utilization.

In practicing the process of the invention, I prefer to flux the ilmenites and titaniferous iron ores with alumina such as to provide, in combination with any alumina naturally present within the ores, an amount within the range 0.25 to 1.0 part by weight (alumina) to each part by weight titania contained within the ores. Optimum fluxing can be achieved within this range at approximately 0.5 part by weight alumina to each part by weight titania. Preferably, fluxing and melting of a reduction burden is effected prior to the addition of any carbonaceous reducing material thereto. Thus, I have found that substantial economies can be realized by withholding 1700 C.). In this manner, the eventual addition of the carbonaceous reducing material results in an extremely rapid reduction reaction with substantially complete separation and settling of entrained metallic iron from the molten slag.

I have found it to be beneficial to employ the ore and alumina in relatively finely-divided forms, and, in

The alumina employed for fluxing purposes can be of any conventional grade and need not be of a particularly high-purity. Advantageously, I may employ a relatively low-grade natural bauxite ore or a non-titaniferous ore contaimng alumina as a principal gangue component, as the fluxing agent, thereby increasing the iron content of the furnace burden while utilizing a relatively inexpensive and plentiful source of alumina.

The components of the furnace charge are so proportioned as to provide reducing agent either in amount just sufiicient for the selective reduction to the metallic state of all of the iron oxide present in the charge, with retention of the titanium values within the resulting slag principally in the form of titanium dioxide, or an excess of carbonaceous reducing agent may be charged to the molten furnace burden and total reduction of iron eifccted with the simultaneous reduction, to any extent desired, of the titanium dioxide content of the charge to lower oxides of titanium, such as Ti O and TiO. Alternatively, over-reduction can be practiced to such an extent as to provide a mixture of divalent titanium monoxide and titanium carbide, exclusively. In actual practice, the degree of reduction effected with respect to the titania content of any furnace burden is regulated in accordance with the particular method of treatment to be used in ultimately processing the resulting slags for recovery of their titanium values. Thus, provided the slags are to be treated by acid leaching, I prefer to effect reduction of as large a quantity as possible of the titanium dioxide to lower oxides while avoiding the formation of any titanium carbide. 'On the other hand, if the slags are to be chlorinated for the selective formation of titanium tetrachloride (TiCl I can practice reduction for the formation of titanium carbide to the greatest extent possible. It is found that such slags can be chlorinated directly, without chlorinating any appreciable portion of the alumina or silica present therein, for the recovery of substantially all of the titanium content of the slag in the form of titanium tetrachloride.

.mentioned copending application Serial No. 553,529,

effecting recovery of both the titania and alumina values actual practice, the ore is crushed, preliminarily, to approximately 8 mesh size or smaller.

present within the slags. In general, this involves crushing of the slag in any suitable manner to approximately mesh size followed by decomposition of the same by digesting at boiling temperatures with sulfuric acid of forty to sixty percent (40-60%) concentration. In lieu of crushing, I have found that the slags may be decomposed (or chlorinated) directly, provided they are granulated with water upon removal from the smelting furnace. In order to facilitate subsequent filtering, the digestion operation is conducted at a temperature of at least 290 C. to dehydrate gelatinous silica. The

sulfuric acid is employed in theoretical quantities plus about ten percent (10%) excess.

Following complete digestion, the hot solution is filtered, washed with sulfuric acid of approximately fifty to sixty percent 50-60%) concentration, and thereafter washed with water. The residue, largely silica, and including impurities, can be discarded. The filtered solution containing titanium sulfate and aluminum sulfate is evaporated to '4060% H 50 and allowed to cool to room temperature (2025 C.) at which point the solubility of aluminum sulfate in H SO of this concentration is very low, and the AI (SO crystallizes out and may be recovered by filtering or centrifuging. The aluminum sulfate, which is a relatively high-purity product, may be marketed as such or converted to high-purity alumina to recoup processing costs, or simply recycled for use as flux in the iron removal stage.

The 60% sulfuric acid solution containing the titanous sulfate may be diluted witlrwater and boiled and the sulfate hydrolyzed to yield titanium hydroxide [Ti(OI-1) which may then be calcined to produce titanium dioxide. The weak sulfuric acid remaining in solution in this type of treatment can be concentrated by evaporation and then recycled to the digestion stage. In lieu of this recovery method, by evaporating the 60% acid to fumes, the titanous sulfate can be recrystallized or salted out and separated by filtering or centrifugingand thereafter decomposed to titanium dioxide and 80 4-80 with the bulk of the strong acid being regenerated and returned to the process in accordance with the technique described and claimed in my copending U.S. application Serial No. 677,454, filed on August 12, 1957, and entitled Process for the Treatment of Metallic Sulfates.

As will be readily appreciated, the unique slags of the invention may be processed by any other conventional method .for recovery of their titanium values. In point of fact, the degree of control provided by the unique fluxing and reduction technique of the invention permits the production of slag products which can be adjusted to optimum composition for treatment by virtually all known processing techniques. .By providing for the sub stantially complete reduction and removal of iron from the slags, coupled with controlled reduction of the titania content without complications in furnace operations, the process of the invention offers a practical and economical solution to the numerous problems presently confronting this industry.

It should be noted .that the process of the invention may be practiced in conjunction with all standard types of furnace apparatus, including electric furnaces as well as oil-fired and gas-fired furnaces, among others. In actual practice for iron removal, however, I prefer to operate within electric arc furnaces of the design and operational characteristics described in my said copending application Serial Number 553,529.

It is believed that the invention may be best understood by reference to the following specific example illustrating the foregoing principles and procedures as applied to the treatment of a titaniferous iron ore of the following analysis:

ORE ANALYSIS Percent TiO 17.15 F203 A1 0 H 9.62 SiO 2.59

Example A charge consisting 0f200 pounds of ore of the foregoing analysis, 12 pounds of alumina, and 34 pounds of coke was smelted within a covered open-arc electric furnace at a temperature of approximately 1650 C. to produce a metallic iron product containing merely trace amounts of titanium, and a molten slag product of the The slag was crushed to 100 mesh or better, and four different fractions were chlorinated at a temperature of 760 C. in the presence of added carbonaceous reducing material (coke of 84% EC.) in amount such that the ratio of slag to coke was to 1. The percentage titanium dioxide chlorinated for the four batches, based on the total available titanium dioxide, was 93 percent, 89.4

percent, 93.8 percent and 95.4 percent. Chlorine con sumption based on alumina and silica present within the slag fractions was negligible in all instances.

What is claimed is:

1. In a process for the treatment of a metallurgical charge comprising at least one material selected from the group consisting of ilmenites, titaniferrous iron ores and concentrates of the same, involving the selective reduction and recovery of metallic iron and the production of an essentially iron-free titania slag therefrom, the improvement that comprises fluxing said charge exclusively with alumina in the production and. furnacing of the reduction burden.

2. In a process for thetreatment of a metallurgical charge comprising at least one material selected from the group consisting of ilmenites, titaniferous iron ores and concentrates of the same, involving the carbothermic reduction and recovery of metallic iron and the production of an essentially iron-free titania slag therefrom, the improvement that comprises fluxing said charge exclusively with alumina in the production and furnacing of the carbothermic reduction burden.

3. In a process for the treatment of a metallurgical charge comprising at least one material selected from the group consisting of ilmenites, titaniferous iron ores and concentrates of the same, involving the selective reduction and recovery of metallic iron and the production of an essentially iron-free titania slag therefrom, the improvement that comprises fluxing said charge for the production of the reduction burden with alumina in an amount sufficient to provide, in combination with any alumina naturally present within the charge from 0.25 to 1.0 part by weight alumina to each part by weight of titania contained therein.

4. In a process for the treatment of a metallurgical charge comprising at least one material selected from the group consisting of ilmenites, titaniferous iron ores and concentrates of the same, involving the carbotherrnic reduction and recovery of metallic iron and the production of an essentially iron-free titania slag therefrom, the improvement that comprises fluxing said charge for the production of the carbothermic reduction burden exclusively with alumina in an amount sufiicient to provide, in combination with any alumina naturally present within the charge, from 0.25 to 1.0 part by weight alumina to each part by weight of titania contained therein.

5. In a process for the treatment of a metallurgical charge comprising at least one material selected from the group consisting of ilmenites, titaniferous iron ores and concentrates of the same, involving the carbothermic reduction and recovery of an essentially iron-free titania slag therefrom, the improvement that comprises fluxing said charge for the production of the carbo'thermic reduction burden exclusively with alumina in the form of a non-titaniferous iron ore containing alumina as a chief gangue constituent thereof such as to provide alumina in an amount within the range 0.25 to 1.0 part by Weight, inclusive of alumina naturally present within the charge, to each part by weight of titania contained therein.

6. In a process for the treatment of a metallurgical charge comprising at least one material selected from the group consisting of ilmenites, titaniferous iron ores and concentrates of the same, involving the carbothermic reduction andrecovery of metallic iron and the production of an essentially iron-free titania slag therefrom, the improvement that comprises fluxing said charge for the production of the carbothermic reduction burden exclusively with alumina in the form of a high-iron bauxite ore such as to provide alumina in an amount within the range 0.25 to 1.0 part by weight, inclusive of alumina naturally present within the charge, to each part by weight of titania contained therein.

7. In a process for the treatment of a metallurgical charge comprising at least one material selected from the group consisting of ilmenites, titaniferous iron ores and concentrates of the same involving the carbotherrnic reduction and recovery of metallic iron and the production of an essentially iron-free titania slag therefrom, the improvements that comprise fluxing said charge solely with alumina in the production of the carbothermic reduction burden, and subjecting the charge and admixed alumina flux to reduction smelting in the presence of sufficient carbonaceous reducing material to eifect reduction to the metallic state of substantially all of the iron oxide contained therein and reduction of a substantial portion of the titania content of said charge to lower oxide forms of titanium.

8. In a process for the treatment of a metallurgical charge comprising at least one material selected from the group consisting-of ilmenites, titaniferous iron ores and concentrates of the same involving the carbothermic re duction and recovery of metallic iron and the production of an essentially iron-free titania slag therefrom, the improvements that comprise fluxing said charge solely with alumina in the production of the carbothermic reduction burden, and subjecting the charge and admixed alumina flux to reduction smelting in the presence of suflicient carbonaceous reducing material to elfect reduction to the metallic state of substantially all of the iron oxide contained therein and reduction of the major portion of the titania content of said charge to lower oxide forms of titanium.

9. In a process for the treatment of a metallurgical charge comprising at least one material selected from the group consisting of ilmenites, titaniferous iron ores and concentrates of the same involving the carbothermic reduction and recovery of metallic iron and the production of an essentially iron-free titania slag therefrom, the improvements that comprise fluxing said charge solely with alumina in the production of the carbothermic reduction burden, and subjecting the charge and admixed alumina flux to reduction smelting in the presence of sutficient carbonaceous reducing material to ellect reduction to the metallic state of substantially all of the iron oxide contained therein and reduction of at least a portion of the titania content of said charge to divalent compounds of titanium selected from the group consisting of titanium monoxide and titanium carbide,

10. In a process for the treatment of a metallurgical charge comprising at least one material selected from the group consisting of ilmenites, titaniferous iron ores and concentrates of the same, involving the carbothermic re- 7 duction and recovery of metallic iron and the production of an essentially iron-free titania slag therefrom, the improvements that comprise fluxing said charge for the production of the carbothermic reduction burden exclusively with alumina in an amount suflicient to provide, in combination with any alumina naturally present within the charge, approximately 0.5 part by weight alumina to each part by weight titania contained therein, and subjecting the charge and admixed alumina flux to reduction smelting in the presence of a carbonaceous reducing material in an amount sufiicient to eltect reduction to the metallic state of substantially all of the iron oxide contained therein and reduction of a substantial portion of the titania content of said charge to lower oxide forms of titanium.

11. In a process for the treatment of a metallurgical charge comprising at least one material selected from the group consisting of ilmenites, titaniferous iron ores and concentrates of the same, involving the carbothermic reduction and recovery of metallic iron and the production of an essentially iron-free titania slag therefrom, the improvements that comprise fluxing said charge for the production of the carbothermic reduction burden exclusively with alumina in an amount sufiicient to provide, in combination'with any alumina naturally present within the charge, approximately 0.5 part by weight alumina to each part by Weight titania contained therein, and subjecting the charge and admixed alumina flux to reduction smelting in the presence of a carbonaceous reducing material in an amount suflicient to elfect reduction to the metallic state of substantially all of the iron oxide contained therein and reduction of the major portion of the titania content of said charge to lower oxide forms of titanium.

12. In a process for the treatment of a metallurgical charge comprising at least one material selected from the group consisting of ilmenites, titaniferous iron ores and concentrates of the same, involving the carbothermic reduction and recovery of metallic iron and the production of an essentially iron-free titania slag therefrom, the improvements that comprise fluxing said charge for the production of the carbothermic reduction burden exclusively with alumina in an amount sufiicient to provide, in combination with any alumina naturally present within the charge, approximately 0.5 part by weight alumina to each part by weight titania contained therein, and subjecting the charge and admixed alumina flux to reduction smelt ing in the presence of a carbonaceous reducing material in an amount suflicient to eflfeot reduction to the metallic state of substantially all of the iron oxide contained therein and reduction of at least a portion of the titania content of said charge to divalent compounds of titanium selected from the group consisting of titanium monoxide and titanium carbide.

13. Process for the treatment of a metallurgical charge comprising at least one material selected from the group consisting of ilmenites, titaniferous iron ores and concentrates of the same that comprises, forming a carbothermic reduction burden by admixing said charge with alumina in an amount of approximately 0.5 part by weight of alumina, inclusive of alumina naturally present within said charge, to each part by weight titania contained therein, subjecting said charge and admixed alumina to reduction smelting in the presence of a carbonaceous reducing agent in an amount at least sufficient to effect reduction to the metallic state of substantially all of the iron oxide contained therein with the production of metallic iron and an essentially iron-free titania slag containing substantially all of the titanium originally present Within said charge, and separating and recovering said metallic iron from said slag product.

14. Process as claimed in claim 13, wherein the carbonaceous reducing agent is added to said reduction burden after the burden'has been established in a molten, fluid state.

Ruzicka Dec. 26, 1939 Wyckofi May 8, 1945 

1. IN A PROCESS FOR THE TREATMENT OF A METALLURGICAL CHARGE COMPRISING AT LEAST ONE MATERIAL SELECTED FROM THE GROUP CONSISTING OF ILMENITES, TITANIFEROUS IRON ORES AND CONCENTRATES OF THE SAME, INVOLVING THE SELECTIVE REDUCTION AND RECOVERY OF METALLIC IRON AND THE PRODUCTION OF AN ESSENTIALLY IRON-FREE TITANIA SLAG THEREFROM, THE IMPROVEMENT THAT COMPRISES FLUXING SAID CHARGE EXCLUSIVELY WITH ALUMINA IN THE PRODUCTION AND FURNACING OF THE REDUCTION BURDEN. 